Schwingungsspektroskopische Untersuchungen zur Chiralitätserkennung und Torsionsdynamik bei Alkoholen
Investigation of Chirality Recognition and Torsional Dynamics in Alcohols by Vibrational Spectroscopy
Robert Medel
Doctoral thesis
Date of Examination:
2020-06-09
Date of issue:
2020-10-20
Advisor:
Suhm, Martin A. Prof. Dr.
Referee:
Suhm, Martin A. Prof. Dr.
Referee:
Mata, Ricardo A. Prof. Dr.
Referee:
Koszinowski, Konrad Prof. Dr.
Referee:
Kruss, Sebastian Dr.
Referee:
Bünermann, Oliver Dr.
Referee:
Schäfer, Tim Dr.
Persistent Address: http://hdl.handle.net/21.11130/00-1735-0000-0005-14BC-1
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Abstract
English
In this thesis different implications of molecular chirality are explored by experimental and quantum chemical methods. Discriminating interactions between molecules of different handedness, termed chirality recognition, are one consequence of chirality. Another one is conformational variety in alcohols due to the accompanying low symmetry. In this context special attention is given to conformational interconversion, including quantum tunneling. To facilitate the comparison with theory, molecular systems are studied in an isolated and cooled condition in supersonic jet expansions. Experimental challenges arise because appropriate model systems, such as alcohol clusters, often feature constituents of low volatility. Strategies to optimize existing techniques and to explore new approaches are therefore another topic of this thesis. OH stretching vibrations are probed by linear FTIR and Raman spectroscopy. Among others, investigated molecular systems include a multitude of monomeric alcohols, clusters of methanol and ethanol up to the hexamer, dimers of benzyl alcohol and 1-phenylethanol as well as mixed dimers of alpha-pinene with different chiral alcohols. Semi-empirical models to predict experimental OH stretching wavenumbers and tunneling splittings of monomeric alcohols are presented. A more extensive summary of the results and a complete overview of investigated systems is available on pages V to IX.
Keywords: chirality recognition; molecular clusters; hydrogen bonding; quantum chemistry; benchmarking; supersonic jet expansion; tunneling splitting; vibrational spectroscopy; FTIR; Raman; alcohol
